Geology
Grand Canyon rock layers from river level looking up
Two Billion Years of Earth History
- Length: 277 miles
- Width: 10 to 18 miles
- Average Depth: 1 mile
- Elevation of Colorado River at Lees Ferry: 3,110 feet
- Elevation of Colorado River at the Grand Wash Cliffs: 1,160 feet
- Drop in Colorado River through the Canyon: 1,950 feet, or 7 feet per mile
- Elevation at Point Imperial on the eastern North Rim: 8,819 feet
- Depth of Canyon below Point Imperial: 6,049 feet
- Elevation of western south rim at Grand Canyon West: 4,768 feet
- Depth of Canyon below Grand Canyon West: 3,568 feet
These are just numbers which cannot do justice to the reality of Grand Canyon. That reality often first strikes visitors as they walk to the edge of the canyon at one of the rim viewpoints. For others, their first view is from a tour airplane or helicopter. Still others see the Grand Canyon from a float trip down the Colorado River or from a trail along the rim or down into the Canyon.
Canyons Carved by Water
For most people, the first impression of the Grand Canyon is of an utterly alien landscape. But if you spend some time at the canyon, slowly the landscape will start to make sense. First of all, you'll see that the canyon is far more than a single canyon. Instead, it is a seeming maze of side canyons, large and small. Look closer, and you'll see that the pattern is not one of chaos, but instead part of an underlying order- an order enforced by the demands of flowing water and gravity.
Plateau Building
Not so obvious are the effects of mountain building forces that lifted the Colorado Plateau high above sea level. These same forces created the Rocky Mountains and provided the headwaters for one of the continent's largest rivers, the Colorado, which in turn, gave the river the power to carve immense canyons from the Colorado Plateau.
The Place
The result is the Grand Canyon of the Colorado River that we see today. But the Grand Canyon is far more than a piece of scenery or a diorama-like view to be glanced at and then discarded. It is a place, a unique portion of the Earth that is a living, breathing ecosystem. If you'll give it some of your time, the Grand Canyon will reward you with some insights into its two billion year history.
Two Billion Years of Rocks
The Grand Canyon is also a geological laboratory where much of the history of the North American continent is preserved as layers of stone exposed in the canyon walls. These rocks range in age from nearly two billion years to several thousand years ago, representing almost half the age of the Earth.
Still Young, Geologically Speaking
The rugged landforms of the Grand Canyon show that it is a geologically young feature. It is still undergoing rapid erosion, as compared to the soft, rounded forms of older geological landscapes such as the Appalachian Mountains. Current theories suggest that the canyon is five to six million years old, but that number is revised frequently in the light of new evidence.
Missing: One Thousand Cubic Miles of Rock
Clearly, the Colorado River removed all of the rock eroded out of the Grand Canyon and carried it off to the Pacific Ocean, but exactly how the river carved such a complex canyon system out of the high plateaus remains the subject of conflicting theories.
Rocks: Geologic Books on a Shelf
Rocks are records of events that took place at the time they formed. They are books. They have a different vocabulary, a different alphabet, but you learn how to read them. -John McPhee